FORM-2
THE PATENTS ACT, 1970
[39 OF 1970]
COMPLETE SPECIFICATION
[See Section 10]
A CONTINUOUS WITHERING SYSTEM FOR PRODUCTION OF BLACK TEA AND
A METHOD THEREOF Applicant
Kilburn Engineering Limited
Plot No 6, MIDC Industrial Area, Saravali
Kalyan Bhiwandi Road, Thane 421 311, Maharashtra, India
An Indian National
The following specification describes the invention and the manner in which it is to be performed.

FIELD OF THE INVENTION:
This invention relates to the field of a continuous withering system for production of black tea, particularly to withering for production of black tea and more particularly to a continuous withering system for production black tea and a method thereof.
BACKGROUND:
Withering is the first and most important step in tea factory in which freshly plucked leaf is conditioned both chemically as well as physically for subsequent processing and can be considered as first step for achieving quality of black tea. In ensure uniform quality with consistent parameters during holding of green leaf without any loss of moisture for chemical wither and later with reduction in moisture during physical withering will improve the quality using continuous withering system. A system with minimum handling of green leaf and consistent parameters (relative humidity and temperature of green leaf) are essential.
To meet the above requirement, continuous withering system with automation can provide the solution to meet the requirement. There is considerable saving in labour cost as well as reduction in space requirement.
At present, various ingenious system like TAT withering, Tunnel withering, Drum withering and Trough withering have been in use.
Trough withering is the most popular system currently being used all over the world because of following reasons:
Economical
Greater flexibility with respect to capacity and degree of wither
Flexibility of construction
Easier operation
Such trough can be used only once in a day due to large holding time for withering of green leaf. After plucking of green leaf, leaf is spread in these rectangular troughs. Lot of manpower is used during spreading of green leaf with holding time for 16 - 18 hours. Axial flow fans are used for blowing atmospheric or conditioned air to get required wither. As atmospheric conditions vary throughout the day, it is difficult to maintain consistence condition in terms of humidity and temperature across the leaf. Excessive manual handling also causes damage to fresh green leaf

results degradation of made tea quality. To ensure uniform quality with consistent parameters, mechanized withering system is the right solution.
Present invention relates to a Continuous withering system which comprises of two separate systems for chemical and physical withering and has separate controls for residence time, humidity and temperature.
Chemical withering starts immediately after plucking. Many chemical changes like production of volatile flavour component, increase in caffeine content, production of organic acid, breakdown of larger organic molecules to simple compounds occur during chemical withering which significantly influences the quality of black tea. The heat generated due to respiration (a process of breakdown of glucose to carbon dioxide and water in presence of oxygen) of the mass of the leaf would heat up the leaves- for this sufficient amount of air is blown though the leaves. The blown air would take away the heat generated and cool down the leaves and also provide necessary supply of oxygen, the latter prevent anaerobic reaction to take place. The product of anaerobic reactions are different and undesirable. Chemical withering normally takes 12-14 hrs and cannot be accelerated.
OBJECT OF THE IVENTION:
The main object of the invention is to obviate the drawbacks in the prior art.
Thus objective of chemical withering is to allow desirable chemical reactions and enzymatic activity to take place in green leaf without heating up, without desiccating leaf and with plenty of oxygen supply. Air mist humidification system will ensure minimum loss of moisture from green leaf. Chemical Withering Bin is designed for keeping the green leaf for required duration with desired parameters of humidity and other control. By controlling humidity and temperature of leaf, green leaf can be kept for minimum 24 hours without any deterioration of colour and quality
After chemical withering, partial withered leaf moves into another set of wire mesh conveyors to reduce the moisture content in leaf. Reduction in moisture level increases the flaccidity of leaf to the desired level.
Desired wither can be achieved by passing conditioned air with respect to atmospheric temperature and humidity conditions. Residence time in holding bin for chemical wither and removal of moisture during physical withering can be varied to achieve the desired parameters.
Comparison between Continuous Withering system of this invention and Existing Manual Withering System
S. Continuous Automatic Withering Batch Manual Withering System
No. System
1. System comprises of separate chemical System comprises of single rectangular and physical section for withering, where trough, where leafs are spread and

leafs are spread and removed using removed manually for further processing,
mechanical conveying system
2. Totally automatic operation -system with Totally manual operation- system
no manual handling of leafs. requires manpower for spreading leafs on
trough and bagging off of leafs from trough.
3. Automatic handling ensures no leaf Manual handling may result in leaf
damage and superior made tea quality in damage during spreading, bagging which
terms of: affects the made tea quality.
• Better infusion
• Better liquor.
• Uniform product quality.
4. Uniform Withering -unaffected by Non uniform withering as it difficult to
weather condition as critical process control the atmospheric conditions,
parameters like relative humidity (RH)
and airflow rate and Residence time in chemical withering bin and air temperature in physical withering bin can be controlled and temp and RH digitally displayed.
5. Negligible physical withering takes place Physical withering in terms of
during chemical withering with desiccation of leafs occur in maintained
controlled temperature and RH and as in dry seasons during chemical
such leafs would remain fresh even at the withering, end of chemical withering.
6. There is negligible rise in leaf There is comparatively higher
temperature during chemical withering. temperature rise of the leaf compared to
Chemical withering section has number the continuous withering system (pilot
of compartments with fan for uniform plant observation)
distribution of air.
7. Continuous system requiring much less Batch system requires much more space space than the batch system. that the continuous system.
8. Chemical withering bin can also act as a Requires repeated turning and piling green leaf storage system- a system to labour intensive.
keep plucked in fresh condition, without any additional manpower.

SUMMARY OF THE INVENTION;
This invention provided a continuous withering method for production of black tea comprising the steps of feeding the fresh plucked green leaf into a double deck vibratory feeder / screen (1) for removal of foreign material from the green leaf,
coveying thus screened green leaf through a cleatted belt conveyors (2) to the feed hopper of a chemical withering bin (3),
adjusting the belt speed therein by frequency drive to ensure filling of gren leaf to the required level in the bin,
spreading the green leafs and preventing them from sticking to each other by distributor of the feed hopper, before leaf falls on the perforated wire mesh conveyor of the chemical withering bin,
maintaining a uniform height of the leaf in the chemical bin by a leaf leveler (7) in the chemical bin,
saturating the air by fine mist of water spray by a spray nozzle (9) fed by pressurized water from a positive displacement pump(10),
sucking almost saturated air by the centrifugal fan(8) in the plurality of segments of the bin and maintaining a relative humidity of 96 -98% using temperature sensor (11) and relative humidity sensors(12),
extracting the leaf from chemical bin by the movement of the wire mesh belt conveyor and discharge vertical pipe conveyor (13) using circular pipe to lift green leaf and taken out the incline guides between pipes,
maintaining the chemical withering time approximately 12 to 16 hours by varying the speed of the conveyor,
conveying the then partial withered leaf into physical withering bin (14) which is a three tier conveyorised system with a provision of uniform hot air supply for removal of moisture,
maintaining the physical withering time between 2-4 hours with 150-180 mm bed height of tea leaf over the conveyor,
obtaining thus the withered leaf.
This invention speaks of a continuous withering system for production of black tea comprising a vibratory conveyor,
a chemical withering bin,
a cleatted belt conveyors ,

a feed hopper of said chemical withering bin,
a distributor inside said feed hopper,
a drive motor at the discharge end of the cleatted belt conveyor with a variable frequency drive,
a levelling screw to level the heap formed on the conveyor by virtue of its flight design,
plurality of segments being formed in the Chemical withering bin ,
a forced draft centrifugal fan (8) provided in each segment,
spray nozzles (9) for production of fine mist to saturate the air sucked by the fans ,
a positive displacement pump (10) to feed the spray nozzles with pressurized water,
temperature sensors (11) and relative humidity sensors (12) being provided to monitor and maintain required hygrometric difference,
a wire mesh belt conveyor and discharge vertical pipe conveyor (13) to take out the green leaves out of the chemical bin.
a physical withering bin (14) which is a three tier conveyorised system with a provision of hot air supply,
BRIEF DESCRIPTION OF THE DRAWINGS
Having thus described the invention in general terms, reference will now be made to the accompanying drawing, which are not necessarily drawn to scale, and wherein:
FIG. 1 shows schematically a diagram of vibratory conveyor of the system.
FIG. la shows Leaf loading into the system.
FIG. 2 shows Cleatted Belt Conveyor of the system.
FIG. 2a shows the feed distributor of the system.
FIG. 2b shows Levelling Screw of the system.
FIG. 3 Centrifugal Aeration Fan of the system.
FIG. 3a : Schematic diagram of fan with spray nozzle of the system.
FIG. 4 shows Chemical Bin of the system with leaf.
FIG.4a shows Pipe Conveyor for Leaf extraction
FIG 5. Shows the Pilot Plant Physical withering Bin

FIG 6: Shows Different components of the Physical withering bin
FIG.7.Shows the flow process of the continuous withering method for production of black tea as per the present invention
DETAILED DESCRIPTION
After receipt of plucked green leaf in nylon bags in factory, green leaf is conveyed to chemical withering section through vibrating conveyor and slit belt conveyor.
There is provision for controlling the inlet humidity and temperature of leaf during chemical withering process.
After holding the leaf for 10 to 12 hours ( from the time of plucking) green chemical withered leaf moves to physical withering three tier conveyor system. Hot air temperature is controlled to 40 - 60°C to control final wither before put into CTC machine.
Working Principle (method) of Continuous Withering Machine:
After plucking and transportation to factory, fresh green leaf is fed into double deck vibratory feeder / screen (1) for removal of foreign material from the green leaf.
A vibratory conveyor is shown in Fig 1. It is a motor driven equipment with an eccentric drive for imparting reciprocating motion for the movement of tea leaves. Tea leaves move on a perforated sheet for removal of foreign material. Leaf loading is shown in Fig la.
After vibratory conveyor green leaf is conveyed through a cleatted belt conveyors (2) to the feed hopper of chemical withering bin (3).
Belt speed is adjusted using frequency drive to ensure filling of green leaf to the required level in the bin. Feed hopper has a distributor in it. The distributor helps spreading the green leafs and prevents them from sticking to each other, especially during rainy season, before leaf falls on the perforated wire mesh conveyor of the chemical withering bin.
Fig 2 shows the cleatted belt conveyor. It has transverse cleats spaced at regular interval to carry the green leafs. It has a drive motor at the discharge end. The speed of the motor could be adjusted with a variable frequency drive.
Fig 2a shows the feed distributor. It is also a motor driven machine placed under the feed hopper. The slow rotating action of the "fingers" helps in spreading the leaves.
The chemical bin also has a leaf leveller 7 to maintain a uniform height of the leaf in the chemical bin
Fig 2b shows a levelling screw, it is a motor driven slow rotating device used to level the heap by virtue of its flight design.
Chemical holding bin is divided into number of segments, each having a forced draft centrifugal fan (8) .The fan sucks almost saturated air produced by fine mist of water spray, to maintain

desired relative humidity of 96 - 98% in the chemical bin. Spray nozzles 9 fed by pressurised water from a positive displacement pump (10) produces fine mist to saturate the air sucked by the fans.
Fig 3 shows centrifugal fans with motor for pumping humidified air to the chemical withering bin. The fans have backward curved blades and have humidification system at the inlet as shown in the schematic diagram in fig 3a.
Temperature sensors (11) and relative humidity sensors (12) are used to monitor and maintain required hygrometric difference.
Leaf is extracted from chemical bin by the movement of the wire mesh belt conveyor and discharge vertical pipe conveyor (13) using circular pipe to lift green leaf and taken out the incline guides between pipes.
Fig 4 shows a chemical bin filled with leaves and 4a shows a pipe conveyor for uniform extraction of leaf from the chemical bin. It is important to note that the system is so designed to prevent any physical damage to the leaf.
Holding time during chemical wither will be approx. 12-16 hours. Holding time can be varied by adjusting conveyor speed.
Partial chemical withered leaf is then conveyed into physical withering bin (14) which is a three tier conveyorised system with a provision of hot air supply. Pilot plant physical withering bin is shown in Fig 5.
Physical withering system, used axial flow fans 15 to push hot air, generated by steam air heater , 16 over the wire mesh type conveyor belt carrying leaf for removal of moisture. Control valve 17 in steam line control the hot air temperature.
Fig 6 shows schematically different component of the physical withering system
For uniform distribution of hot air an air plenum 18 and distribution plates 19 are provided for the entire length of the conveyorised system .
Residence time during physical wither can be varied between 2-4 hours with 150 - 180 mm bed height of tea leaf over the conveyor.
The withered leaf coming out of physical withering bin goes to the process.
FIG.7.Shows the flow process of the continuous withering method for production of black tea as per the present invention
SYSTEM COMPONENT DETAILS
Chemical Withering Bins

Hold up capacity for sixteen hours duration (holding capacity 20,000 kg.)
Humidity level to be maintained as 96-98%
Discharge pipe conveyor weir (special configuration)
Conveyor system for movement and support of green leaf
Provisions of water spray mist to maintain humidity condition using forced draft fan system.
Leveler for maintaining level and lump breaker to handle green wet leaf during rainy season.
System include temperature and humidity sensors to control relative humidity in the system.
Physical Withering Bin with 3 tier conveyor belt
3 tier conveyorised system for drying of chemical withered green leaf
Air permeability fabric belt conveyor in three stage with uniform air flow pattern for the entire length of 3 tier conveyor for physical withering of green leaf
Sealing arrangement to avoid short circuiting of hot air in three stage conveyor
Hot air system comprising of axial flow fan with sufficient head and steam radiator to raise the temp, of atmospheric air for drying. Hot air temp, depends upon weather condition and it's valve will be in the range of 40-60°C.
- Residence time during physical wither - 2 hrs. (min.)
Major Advantages of Continuous Withering System
-Very good control over the process parameters like humidity and temperature of leaf which results uniform withering of green leaf.
-It is easier to control loading / unloading of green leaf. Holding time in respective sections can be controlled which results better leaf quality.
-No manual handling of green leaf, results no damage to green leaf and ensure better quality of final made tea.
-Saving in manpower requirement. No spreading/ refilling of withered leaf in bags for further processing of green withered leaf.
-Expected manpower requirement will be 2 to 3 nos. (max.)
- Compact system. Approximate space requirement will be 1/3 as compared
manual trough system for similar capacity.
Salient Features
-Flexibility in operation by controlling parameters like humidity and temperature of green leaf, plucked leaf can be hold for longer duration

-Easily control of wither condition of green leaf.
-No manual handling of green leaf. Green leaf automatically moves from
chemical wither section to physical wither section at controlled rate for further
processing.
-Stainless steel construction for chemical wither section to ensure no corrosion due to handling wet green leaf and high humidity condition.
- Thick conveyor belt used for carrying green leaf ensure long life. -Instruments incorporated to provide information about moisture loss in green leaf which is important for quality of wither.
-Chemical and physical withering sections have number of compartments for uniform distribution of air.
The present invention is not limited to the above-described embodiments, and various alterations,
modifications, and/ or alternative applications of the invention may be possible, if desired,
without departing from the scope and sprit of the invention, which can be read from the claims
and the entire specification. All these possible alterations, modifications, and /or alternative
applications of the invention are also intended to be within technical scope of the present
invention.

We Claim:
\ A continuous withering method for production of black tea comprising the steps of feeding the fresh plucked green leaf into a double deck vibratory feeder / screen (1) for removal of foreign material from the green leaf,
covey ing thus screened green leaf through a cleatted belt conveyors (2) to the feed hopper of a chemical withering bin (3),
adjusting the belt speed therein by frequency drive to ensure filling of green leaf to the required level in the bin,
spreading the green leafs and preventing them from sticking to each other by distributor of the feed hopper, before leaf falls on the perforated wire mesh conveyor of the chemical withering bin,
maintaining a uniform height of the leaf in the chemical bin by a leaf leveler (7) in the chemical bin,
saturating the air by fine mist of water spray by a spray nozzle (9) fed by pressurized water from a positive displacement pump(l 0),
sucking almost saturated air by the centrifugal fan(8) in the plurality of segments of the bin and maintaining a relative humidity of 96 -98% using temperature sensor (11) and relative humidity sensors(12),
extracting the leaf from chemical bean by the movement of the wire mesh belt conveyor and discharge vertical pipe conveyor (13) using circular pipe to lift green leaf and taken out the incline guides between pipes,
maintaining the chemical withering time approximately 12 to 16 hours by varying the speed of the conveyor,
conveying the then partial withered leaf into physical withering bin (14) which is a three tier conveyorised system with a provision of uniform hot air supply for removal of moisture,
maintaining the physical withering time between 2-4 hours with 150 - 180 mm bed height of tea leaf over the conveyor,
obtaining thus the withered leaf.
2. A continuous withering system for production of black tea comprising a vibratory conveyor,
a chemical withering bin,
a cleatted belt conveyors ,
a feed hopper of said chemical withering bin ,

a distributor inside said feed hopper,
a drive motor at the discharge end of the cleatted belt conveyor with a variable frequency drive, a levelling screw to level the heap formed on the conveyor by virtue of its flight design, plurality of segments being formed in the Chemical withering bin ,
a forced draft centrifugal fan (8) provided in each segment,
spray nozzles (9) for production of fine mist to saturate the air sucked by the fans ,
a positive displacement pump (10) to feed the spray nozzles with pressurized water,
temperature sensors (11) and relative humidity sensors (12) being provided to monitor and maintain required hygrometric difference,
a wire mesh belt conveyor and discharge vertical pipe conveyor (13) to take out the green leaves out of the chemical bin.
a physical withering bin (14) which is a three tier conveyorised system with a provision of hot air supply,
3. A continuous withering system for production of black tea according to claim 2 wherein the vibratory conveyor is a motor driven equipment with an eccentric drive for imparting reciprocating motion for the movement of tea leaves.
4. A continuous withering system for production of black tea according to claims 2 or 3 wherein the cleatted belt conveyor has transverse cleats spaced at regular interval to carry the green leafs and has a drive motor at the discharge end and variable frequency drive to adjust the speed of said motor.
5. A continuous withering system for production of black tea according to claims 2 to 4 wherein the feed distributor is also a motor driven machine placed under the feed hopper and the slow rotating action of the "fingers" helps in spreading the leaves.
6. A continuous withering system for production of black tea according to any of the claims 2 to 5 wherein the centrifugal fans with motor for pumping humidified air to the chemical withering bin have backward curved blades and have humidification system at the inlet as shown in the schematic diagram in fig 3a.
7. A continuous withering system for production of black tea according to any of the preceding claims wherein the physical withering bin (14) has axial flow fans (15) to push hot air generated by steam air heater, 16 over the wire mesh type conveyor belt carrying leaf for removal of moisture and a Control valve 17 in steam line control the hot air temperature.

8. A continuous withering system for production of black tea according to any of the preceding claims wherein the physical withering bin (14) has air plenum (18) and distribution plates (19) for the entire length of the conveyorised system for uniform distribution of hot air.
9. A continuous withering system for production of black tea according to any of the preceding claims wherein the leveling screw is a motor driven slow rotating device used to level the heap by virtue of its flight design.